The pollen morphology of all 24 species of the genus Macrotyloma is very distinctive and is unique in the subfamily Papilionoideae. The tectum is finely rugulate with supratectal tubercles, spines, bacula or clavae. There is a very thick endexine, no foot layer, very short dense columellae and very thin tectum. There are two aperture types, tricolporate and triporate. The taxonomically least specialised species M. ciliatum, M. decipiens and M. maranguense have tricolporate pollen while the remaining more derived species have triporate pollen.